private void buttonSave_Click(object sender, EventArgs e)
        {
            try
            {
                if (buttonSave.Text.Equals("Confirm"))
                {
                    int updateQuantity = Convert.ToInt32(textBoxStockInQuantity.Text);
                    _item.AvailableQuantity += updateQuantity;
                    _stockIn.Quantity        = updateQuantity;
                    _stockInManager.UpdateAvailableQuantity(_item);
                    _stockInManager.UpdateStockIn(_stockIn);
                    buttonSave.Text = "Save";
                }
                else
                {
                    if (comboBoxCompanyName.Text.Equals("-Select-"))
                    {
                        MessageBox.Show("Enter a company!");
                        return;
                    }
                    if (comboBoxCategoryName.Text.Equals("-Select-"))
                    {
                        MessageBox.Show("Enter a category");
                        return;
                    }
                    if (comboBoxItemName.Text.Equals("-Select-"))
                    {
                        MessageBox.Show("Enter an Item");
                        return;
                    }
                    _stockIn.Date   = dateTimePickerUserDefineDate.Value.ToString("yyyy-MM-dd");
                    _stockIn.ItemID = Convert.ToInt32(comboBoxItemName.SelectedValue);
                    if (String.IsNullOrEmpty(textBoxStockInQuantity.Text))
                    {
                        MessageBox.Show("Enter a quantity!");
                        return;
                    }
                    _stockIn.Quantity = Convert.ToInt32(textBoxStockInQuantity.Text);
                    AddStockIn(_stockIn);

                    //update avaiableQuantity
                    _item.ID   = _stockIn.ID;
                    _dataTable = _stockInManager.GetItemById(_item);
                    int currentQuantity = Convert.ToInt32(_dataTable.Rows[0]["AvailableQuantity"]);
                    _item.AvailableQuantity = currentQuantity + _stockIn.Quantity;
                    _stockInManager.UpdateAvailableQuantity(_item);
                }


                TextBoxDefaultValue();
                textBoxStockInQuantity.Text = "";

                DisplayAllRecords();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
        protected void itemDropDownList_SelectedIndexChanged(object sender, EventArgs e)
        {
            ItemViewModel aItemViewModel = new ItemViewModel();
            int           ItemId         = Convert.ToInt32(itemDropDownList.SelectedItem.Value);

            aItemViewModel                = aStockInManager.GetItemById(ItemId);
            reorderLevelTextBox.Text      = aItemViewModel.ReorderLevel.ToString();
            availableQuantityTextBox.Text = aItemViewModel.Quantity.ToString();
        }